This invention relates to a rocker arm arrangement for a single cam multiple valve engine and more particularly to an improved, compact rocker arm arrangement for operating multiple valves of an engine from a single camshaft and permitting varying degrees of lift and valve events for the valves.
The use of multiple valves for a single combustion chamber of an internal combustion engine has been acknowledged to provide an increase power output for the engine in relation to a given displacement. However, when multiple valves are employed, there becomes considerable difficulty in both the placement and actuation of the valves. In one widely use form of multiple valve engine, there are provided a pair of camshafts each of which operates all of the intake or exhaust valves. Such engines are normally called DOHC engines. This type of engine permits a fairly wide latitude in valve placement and valve events. Also, it accommodates providing different valve events or different lifts for the individual valves operated by each camshaft since each valve is normally operated by its own lobe. However, this type of engine is bulky and can be expensive.
Another type of multiple valve engine (SOHC) uses a single overhead mounted camshaft for operating all of the valves. Normally, a series of rocker arms are provided for operating the intake and exhaust valves from the single overhead mounted cam. However, in addition to the positioning of the camshaft and valve actuating, it is also necessary to position one or more spark plugs for each combustion chamber in the cylinder head. This further complicates the engine construction.
In order to provide a more compact and simpler assembly, it has been proposed to operate more than one valve from a single rocker arm. Such an arrangement, obviously, provides simplification of the engine. However, when more than one valve is operated by a single rocker arm then the valves that are commonly actuated normally must have the same valve events and the same valve lift. Although the lift may be varied slightly by changing the length of the portions of the rocker arms that engage the individual valves, there are limitations to such variations. In addition, the use of such compound rocker arms results in expensive rocker arm cost due to the difficulty in forming such complicated rocker arm configurations.
It is, therefore, a principal object to this invention to provide an improved rocker arm arrangement for operating multiple valves of a single overhead camshaft engine.
It is a further object to this invention to provide an improved and compact assembly for operating multiple valves of a single overhead camshaft engine while permitting latitude in the individual events of the various valves.
It is a further objection to this invention to provide a compact and yet versatile single overhead cam multiple valve engine.